The present invention relates to a precise positioning actuator for a head element such as a thin-film magnetic head element or an optical head element, to a head gimbal assembly (HGA) with the actuator and to a manufacturing method of a precise positioning actuator.
In a magnetic disk drive apparatus, thin-film magnetic head elements for writing magnetic information into and/or reading magnetic information from magnetic disks are in general formed on magnetic head sliders flying in operation above the rotating magnetic disks. The sliders are supported at top end sections of suspensions of HGAs, respectively.
Recently, recording and reproducing density along the radial direction or along the track width direction in the magnetic disk (track density) rapidly increase to satisfy the requirement for ever increasing data storage capacities and densities in today""s magnetic disk drive apparatus. For advancing the track density, the position control of the magnetic head element with respect to the track in the magnetic disk by a voice coil motor (VCM) only has never presented enough accuracy.
In order to solve this problem, an additional actuator mechanism is mounted at a position nearer to the magnetic head slider than the VCM so as to perform fine precise positioning that cannot be realized by the VCM only. The techniques for realizing precise positioning of the magnetic head are described in for example U.S. Pat. No. 5,745,319 and Japanese patent publication No. 08180623 A.
As for a precise positioning actuator, there are various structures of actuator such as for example a load-beam structure actuator and a piggy-back structure actuator.
The load-beam structure actuator has two piezoelectric elements of PZT attached on a load beam of a suspension. These PZT elements are driven in a manner to support with each other to displace the load beam so as to perform fine precise positioning of a magnetic head slider mounted on the load beam.
The piggy-back structure actuator is formed by piezoelectric material of PZT in an I-character shape with one end section to be fixed to a suspension, the other end section to be fixed to a magnetic head slider and a pillar shaped movable arm connected between these end sections. The PZT is driven to perform fine precise positioning of the magnetic head slider directly attached to this actuator. On the suspension, stepwise stacked are the actuator and the magnetic head slider, namely, the actuator is caught between the suspension and the slider to form a stacked cantilever structure.
However, the aforementioned conventional precise positioning actuators had following various problems:
(1) Mechanical resonance was occurred at a relatively low frequency;
(2) Since the actuator as a whole consists of piezoelectric material such as PZT of a brittle material, shock resistance is very poor. Particularly, since in case of a piggy-back structure actuator, the actuator and the magnetic head slider are stacked to form a cantilever structure, a shock easily occurs with a moment and also shock resistance is extremely poor;
(3) Depending upon the size of the magnetic head slider, a travel of the magnetic head element during the precise positioning operation varies. Thus, it is difficult to obtain enough stroke;
(4) Handling at the tire of an assembly of the HGA is very difficult;
(5) Particularly, in case of a piggy-back structure actuator, because of the stepwise stacked structure, a total thickness of the HGA around the magnetic head slider increases by the thickness of the actuator;
(6) In case of a piggy-back structure actuator, because of three-dimensional and complicated attachment structure, the handling at the time of an assembly of the HGA is extremely difficult and it is impossible to use a conventional HGA assembly equipment causing productivity to be very worse; and
(7) In order not to interfere with the movement of the piggy-back structure actuator, it is necessary to assemble with keeping a gap between the actuator and the magnetic head slider and also between the actuator and the suspension. However, forming of such gaps will more decrease the shock resistance and it is difficult to precisely keep the gaps constant. Particularly, since it is difficult to keep the suspension, the actuator and the magnetic head slider in parallel precisely, the head characteristics deteriorates.
To solve the aforementioned various problems, the inventors of this application had proposed an actuator provided with a pair of metal plate movable arms for fixing and catching a magnetic head slider in a space between the movable arms (U.S. Pat. Ser. No. 09/972,939 now pending).
This proposed actuator is fabricated by cutting each pattern for the actuator from a metal plate and by bending the pattern along predetermined lines to form a three-dimensional structure of the actuator. However, since the metal plate used for the movable arms of the actuator must have a relatively large thickness of about 50 to 70 xcexcm, it is very difficult to correctly bend the pattern of metal plate along precise lines at a precise angle.
It is therefore an object of the present invention to provide a precise positioning actuator for a head element, an HGA with the actuator and a manufacturing method of a precise positioning actuator, whereby the actuator can be fabricated without bending a metal plate.
According to the present invention, a precise positioning actuator to be fixed to a head slider provided with at least one head element and to a support, for precisely positioning the at least one head element includes a pair of movable arms and a base section. Each movable arm is formed by a plate member including a first metal plate to be substantially in parallel with a side surface of the head slider. Top end sections of the pair of movable arms are capable of displacing in response to a drive signal applied to the actuator along a direction crossing planes of the metal plates. The base section is connected between rear end sections of the pair of movable arms and formed by a plate member including a second metal plate. The base section and the pair of movable arms are formed by adhering the first metal plates and the second metal plate that are individually formed. Also, according to the present invention, an HGA includes a head slider provided with at least one head element, a support and this precise positioning actuator fixed to the head slider and to the support for precisely positioning the at least one head element.
Since the base section and the pair of movable arms are formed by adhering metal plates that are individually formed, it is possible fabricate them without bending a metal plate. Therefore, the fabrication of the actuator becomes easy and a high precision actuator can be obtained.
Also, the movable arms and the base section are mainly made from a metal plate, the weight of the whole actuator can be reduced and thus a mechanical resonance frequency of the actuator can be increased. Further, as a basic member of the arms is formed by the metal plate that is strong and light-weighted, a shock resistance of the movable arms that are particularly weaken for the shock can be greatly improved. Due to the usage of the metal plate provided with a high mechanical strength, treatment of the actuator during assembling of the HGA becomes very easy. By using the metal plate to form the main portion of the actuator, the flexibility on a design of the actuator will improve with the shape and/or size. Thus, it is enabled to design the actuator with a sufficient stroke. Furthermore, because the metal plate can be precisely machined, accuracy in size of the actuator itself can be greatly improved.
Also, since the head slider will be mounted in a space between the movable arms, the thickness of the HGA around the head slider (Z-height) does not increase even if the actuator is attached. Thus, no modifications in size of the disk drive apparatus due to the mounting of the actuator is necessary. In addition, since the head slider is caught in between the movable arms, the top end sections of the movable arms, which actually transfer the displacement to the slider, can be extended to always position at the top end of the slider. Thus, it is possible to provide a constant travel to the slider even if the size of the head slider changes, and therefore an enough stroke of the head at the precise positioning operation can be always obtained.
It is preferred that a resin layer is laminated on outer surfaces of the pair of able arms and the base section.
It is also preferred that the actuator further includes spacers formed on inner surfaces of the top end sections of the pair of movable arms, the spacers being to be fixed to the side surfaces of the head slider so as to provide air gaps between the side surfaces of the head slider and the pair of movable arms, respectively. Since the side surfaces of the head slider does not contact with the movable arms due to the air gap provided by the spacers, displacement of the head slider becomes free. In this case, the spacers may be individually formed from the pair of movable arms, or formed by a part of a resin layer of the movable arm.
It is further preferred that the actuator further includes a coupling section connected between the top end sections of the pair of movable arms and substantially in parallel with an upper surface of the head slider. The upper surface that is opposite to an air bearing surface (ABS) is to be fixed to the coupling section. Since the actuator is provided with a coupling section connected between the top end sections of the pair of movable arms and the head slider is to be fixed to this coupling section, fixing of the slider can be achieved with sufficient strength and a shock resistance against up-and-down movements can be greatly improved. Also, head sliders with different widths can be easily mounted to the actuator.
It is preferred that the coupling section is formed only by a resin layer.
It is also preferred that the pair of movable arms, the base section and the coupling section have a U-shaped section structure.
It is preferred that the resin layer is a polyimide resin layer. Also, preferably, the metal plate is a stainless steel plate.
It is further preferred that each of the pair of movable arms includes an arm member made of the plate member including the metal plate, and a piezoelectric element formed or adhered on a side surface of the arm member.
It is preferred that the at least one head element is at least one thin-film magnetic head element.
According to the present invention, furthermore, a manufacturing method of a precise positioning actuator to be fixed to a head slider provided with at least one head element and to a support, for precisely positioning the at least one head element, the method includes a step of forming, from a plate member fabricated by laminating at least one resin layer and at least one metal plate, a pair of movable arms each including a part of the at least one metal plate and a displacement generation element formed on one surface of the movable arm, and a base section connected between rear end sections of the pair of movable arms and including a part of the at least one metal plate separated from the parts of the at least one metal plates of the pair of movable arms by a predetermined space, a step of forming, from the plate member, a base section coupling member made of the at least one resin layer to couple the pair of movable arms and the base section, a step of bending the base section coupling member so that the pair of movable arms become substantially perpendicular to the base section, and a step of adhering the base section and the pair of movable arms with each other under the bending state of the base section coupling member.
The metal plate for the movable arms and the metal plate for the base section are formed to be separated themselves by a predetermined space but coupled by means of the resin layer, then the resin layer is bent so that the movable arms become substantially perpendicular to the base section, and the base section and the movable arms are adhered to each other under the bending state. Since the metal plates are separated and the resin layer for coupling the metal plates is bent, it is possible fabricate the actuator without bending the metal plates. Therefore, the fabrication of the actuator becomes easy and a high precision actuator can be obtained.
It is preferred that the method further includes a step of forming spacers on inner surfaces of top end sections of the pair of movable arms, the spacers being to be fixed to side surfaces of the head slider so as to provide air gaps between the side surfaces of the head slider and the pair of movable arms, respectively. Since the side surfaces of the head slider does not contact with the movable arms due to the air gap provided by the spacers, displacement of the head slider becomes free. In this case, the spacers forming step may include etching the plate member to remain parts of the resin layers of the pair of movable arms, or include preparing members individually formed from the pair of movable arms, and adhering the members to the inner surfaces of the top end sections of the pair of movable arms.
It is also preferred that the method further includes a step of forming a coupling section connected between top end sections of the pair of movable arms and substantially in parallel with an upper surface of the head slider. The upper surface that is opposite to an air bearing surface (ABS) is to be fixed to the coupling section.
It is further preferred that the coupling section is made of only the at least one resin layer.
It is preferred that the predetermined space of the metal plates is larger than a thickness of the at least one metal plate. If the space is less than the thickness of the at least one metal plate, the metal plates cannot be perpendicularly adhered to each other. Contrary to this, if the space is too large, the resin layer may sag and it may be difficult to adhere the metal plates in perpendicular.
It is also preferred that the base section is formed by folding the at least one metal plate. If the metal plate for the base section and the movable arms are patterned by etching, side edges of the metal plates are formed in tapered shapes. Thus, it will be difficult to perpendicularly fix the metal plates to each other. However, if the base section is formed by folding the at least one metal plate, tops of the side edges of both the folded metal plates abut to the metal plate members for the movable arms when bending. Thus, it is easy to perpendicularly fix the metal plate for the base section and the metal plate members for the movable arms to each other.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the a carrying drawings.